1. Field of the Invention
The present invention relates to improvements of a disc driving device for a disc storage(memory) system used for computers.
2. Description of the Related Art
Presently, in order to rotate a storage disc in a sealed housing of disc storage systems employing such as "Hard Disc" (referred to as "HD") or "Magneto-Optical Disc", a disc driving device is widely used in such a disc driving systems.
In the disc driving device for driving such as an HD comprised of a hard material substrate and a magnetic layer thereon, the HD is sealed together with a flying head within a housing for recording and reproducing signals on and from the HD.
FIG. 1 is a cross sectional view of main part of an example of a disc driving device using HDs in a prior art.
FIG. 2 is a cross sectional view of main part of another example of a disc driving device using HDs in a prior art.
Referring to FIG. 1, provided in a sealed housing 203 of a disc driving device 200, are a hub 206 on which a plurality of HDs 205 is coaxially mounted, and ring spacers 211 are interposed between the HDs 205, and other components such as flying heads (not shown).
The sealed housing 203 comprises a housing 202 having an upper opening covered with a top plate 201, and a lower opening. A spindle motor 208 rotating the hub 206 generally comprises an outer rotor 208a and a stator having a stator frame 210 (described hereafter) which covers the lower opening of the housing 202 so that the outer rotor 208a protrudes from the housing 202 through the lower opening. The hub 206 is coaxially mounted at the distal end of the spindle 207 which is rotatably supported from the stator frame 210 by bearings 204 provided at an inner wall of the stator frame 210. Further, the sealed housing 203 is sealed by a magnetic fluid seal 209 provided between the inner wall of stator frame 210 and the spindle 207 so as to prevent dust from invading the sealed housing 203 through the outer rotor 208a which is exposed to the external atmosphere. In the above mentioned disc driving device 200, the flying heads float from the rotating HDs 205 at a predetermined distance and perform recording and reproducing of signals on/from the rotating HDs 205 within the sealed housing 203. Referring to FIG. 2 illustrating another disc driving device 300, a hub 309 on which a plurality of HDs 304 is coaxially mounted, and ring spacers 310 are interposed between the HDs 304. Other components such as flying heads (not shown) and a spindle motor 305 are provided together with the hub 309, the HDs 304 and spacers 310, all within in a sealed housing 303. The sealed housing 303 comprises a housing 302 having an upper opening closed with a top plate 301, a lower opening closed with a stator frame 306 of the spindle motor 305, so that the stator frame 306 protrudes into the housing 302. A spindle 307 is supported from the stator frame 306 by bearings 311 provided at an inner wall thereof. The sealed housing 303 is sealed by a seal member 308 at an opening provided at a bottom of the stator frame 306 through which the bearings 311 are installed.
In the operation of the above mentioned disc driving device 300, the flying heads float from the rotating HDs 304 at a predetermined distance and perform recording and reproducing of signals on/from the rotating HD 304 within the sealed housing 303.
In the first example of the prior art device 200 shown in FIG. 1, there present problems that it needs the magnetic fluid seal 209 between the stator frame 210 and the spindle 207 to prevent dust from invading the sealed housing 203 so that it requires a rather complicated structure. Further, the large lower opening provided in the housing 202 for mounting the stator frame 210 decreases the mechanical strength of the housing 202.
In the second example of the prior art device 300 in shown FIG. 2, there also presents a problem that a motor core 305a which is exposed in the sealed housing 303, is liable to get rusty in an extended use becoming a source of dust. In order to eliminate this problem, the motor core 305a is normally coated with a layer of epoxy resin having a thickness from 50 to 60 .mu.m, this increases a gap Between the motor core 305a and a rotor magnet 305b causing the efficiency of the spindle motor to degrade.